Many drugs which affect behavior also profoundly affect monoaminergic neurons in the brain and in peripheral tissues. Although effects of the acute administration of these drugs have been studied extensively, there are few studies which involve the prolonged administration of such drugs. The actions of many of these drugs differ considerably depending upon whether they are administered acutely or are administered repeatedly over a prolonged period of time. For example, the repeated administration of narcotic analgesics results in the development of tolerance to certain specific effects of these drugs. Animals also become physically dependent upon narcotic analgesics. The purpose of the proposed project is to compare the effects of acute and chronic administration of certain drugs which affect behavior upon the uptake, synthesis, storage, metabolism and release of biogenic amines in the brain and by adrenergic neurons in peripheral tissues. Three classes of drugs will be studied: the narcotic analgesics, the psychomotor stimulants and the tricyclic antidepressants.